1. Field of the Invention
The present invention relates to a system for conveying ceramic shaped bodies on and along a conveying path in the state that the ceramic shaped bodies are placed on cradles. The present invention also relates to such cradles used for the conveying system.
2. Description of the Related Art
Heretofore, the following process is known as an example of a process for producing ceramic products such as ceramic honeycomb structural bodies. Firstly, ceramic shaped bodies are obtained by molding a ceramic material and cut in a given length. Then, the cut ceramic shaped bodies are individually placed on cradles, and the cradles on which the ceramic shaped bodies are placed are moved along a conveyor path. After that, a given number (for example, five) of the ceramic shaped bodies are aligned and dried, and both end faces of the dried ceramic shaped bodies are cut and finish worked. Finally, the thus finish worked ceramic shaped bodies are fired to obtain ceramic products.
In the above conventional process for producing ceramic honeycomb structural bodies, when the ceramic shaped bodies are placed on the cradles and conveyed, the conveyor path needs, in some cases, to change its conveying direction on the way due to a downstream process layout such as a factory layout or a dryer layout. In this case, it is conventional that the cradles are stopped at a terminal end of a first conveyor path by bumping them against a stopper, and the cradles are pushed to another conveying direction by a plunger or the like to transfer to the next conveyor path. In addition, it is necessary to align two or more ceramic shaped bodies on the conveyor path before entering to the drying step. In this case, also, the cradle is conventionally stopped at the terminal end of the conveyor path by bumping it against a stopper, then the next cradle bumps against the stopped cradle, and this operation continues until the cradles at least required for aligning are acquired.
In the above conventional system for conveying ceramic shaped bodies, when the green ceramic honeycomb shaped bodies are conveyed, shock of bumping upon stopping or changing the conveying direction of the ceramic shaped bodies, or shock caused by the plunger upon pushing is applied on the ceramic shaped bodies. However, even if such a shock is applied, since ceramic honeycomb shaped bodies having a cell-wall thickness of about 150 xcexcm, which are conventionally used, have high strengths, the ceramic honeycomb shaped bodies are not deformed, cracked or broken. Therefore, final ceramic products can be obtained without any problems.
However, thin-walled ceramic honeycomb shaped bodies having a cell-wall thickness of 120 xcexcm or less and a cell density of about 400-1600 cell/sq. in., which have been highly demanded these days, are much weaker than the conventional shaped bodies especially in the green state. Thus, when the thin-walled ceramic honeycomb shaped bodies are conveyed with a conventional system for conveying ceramic shaped bodies, the ceramic shaped body are deformed, cracked or, in an extreme case, even broken with a shock of bumping upon stopping or changing the conveying direction of the ceramic shaped bodies, or a shock caused by the plunger upon pushing. In addition, the strengths of the thin-walled ceramic honeycomb shaped bodies have directionality. It is strong against an impact in the axis direction, relatively strong against an impact in the vertical direction to the cradle as it is supported by the cradle, and extremely weak against an impact in the horizontal direction.
It is an object of the present invention to solve the aforementioned problems and provide a system for conveying ceramic shaped bodies and cradle used for the system without any deformations, cracks or breakages of the thin-walled ceramic shaped bodies upon conveying.
A first aspect of the system for conveying ceramic shaped bodies according to the present invention is the system for conveying ceramic shaped bodies on and along a conveyor, said system comprising cradles, a conveyor comprising first and second conveyor paths and a conveying direction-changing station, the ceramic shaped bodies being placed on the cradles and the cradles being conveyed on and along the conveyor, wherein a conveying direction of the ceramic shaped body is changed at the conveying direction-changing station while an impact on the ceramic shaped body is absorbed by lifting up the cradle from the first conveyor path, transferring the cradle to the second conveyor path having a different conveying direction from that of the first one while keeping the cradle lifted, and then putting down the cradle on the second conveyor path.
A second aspect of the system for conveying ceramic shaped bodies according to the present invention is the system for conveying ceramic shaped bodies on and along a conveyor, said system comprising cradles and a conveyor, said ceramic shaped bodies being placed on said cradles and said cradles being conveyed on and along said conveyor, wherein the ceramic shaped bodies are stopped while impacts on the ceramic shaped bodies are absorbed by gradually reducing the conveying speed of the cradles on the conveyor to stop the cradle, when the cradles on which the ceramic shaped bodies are to be placed are stopped on the way of the conveyor.
In the aforementioned systems for conveying ceramic shaped bodies, the impact on the ceramic shaped bodies can be absorbed by, according to the first aspect, lifting up the cradle from the first conveyor path, transferring the cradle to the second conveyor path having a different conveying direction from that of the first one while keeping the cradle lifted, and then putting down the cradle on the second conveyor when the conveying directions of the cradles on which the ceramic shaped bodies are placed are changed on the way of the conveyor, or by, according to the second aspect, gradually reducing the conveying speed of the cradles on the conveyor to stop the cradle on the way of the conveyor when the cradles on which the ceramic shaped body placed is stopped on the way of the conveyor. Accordingly, deformations, cracks and breakages of the ceramic shaped bodies during conveying can be prevented.
Further, the cradle used for the system for conveying the ceramic shaped bodies according to the present invention comprises a base preferably made of aluminum, a supporting member provided on the base, preferably made of foamed polystyrene, and having a receiving portion that is formed on a side opposed to the side contacting the base and is shaped corresponding to a shape of the ceramic shaped body, and a cushioning material provided to cover the receiving portion of the supporting member, whereby the cradle is to convey the ceramic shaped body while absorbing an impact on the ceramic shaped body.
In the aforementioned cradles used for conveying ceramic shaped bodies according to the present invention, the ceramic shaped body can be received by the receiving portion of the foamed polystyrene supporting member of the cradle and the cushioning material covering the receiving portion. Therefore, even when a shock is applied on the ceramic shaped body, an impact can be effectively absorbed. In addition, since the ceramic shaped body is held in a state that the cushioning material contacts the ceramic shaped body, the ceramic shaped body can be easily released from the cradle, the supporting member made of the easy-to-break, foamed polystyrene can be prevented from breaking, and thus the cradle can be reused. Moreover, by making the base from aluminum, the entire cradle can be made light and less costly. Furthermore, by making the supporting member from foamed polystyrene, the entire cradle can be made light and less costly to make handling and attaching/detaching easy. As well, since the cradle can be easily worked, even if a diameter of the ceramic shaped body to be held is not the same as being expected due to a difference in shrinking factor, the supporting member can be worked afterward to hold such a ceramic shaped body if the diameter is larger than the expected one. The cushioning material is used for preventing the ceramic shaped body to be held from sliding too much and disturbing a slipping movement due to a large frictional resistance. In addition, the supporting member made of easy-to-break foamed polystyrene may be used in the cradle with the aforementioned configuration, since the cradle contacts the conveyor path via the aluminum base.